1. Field of the Invention
The present invention relates to a refrigerant cycle system having a hot-gas bypass structure, in which hot gas refrigerant discharged from a compressor is directly introduced into an evaporator after being decompressed while bypassing a condenser during a heating mode. The refrigerant cycle system accurately determines a refrigerant shortage during the heating mode, and is suitable for a vehicle air conditioner.
2. Description of Related Art
In a conventional vehicle air conditioner, air blown into a passenger compartment is heated by using hot water (engine-cooling water) flowing through a heating heat exchanger as a heating source during a heating mode in the winter. In this case, when temperature of hot water is low, the temperature of air blown into the passenger compartment is lowered, and heating capacity for the passenger compartment becomes insufficient.
JP-A-5-272817 describes a refrigerant cycle system which can set a heating mode using a hot-gas refrigerant bypassing structure. In the conventional system, when temperature of hot water is lower than a predetermined temperature at an engine start time, hot-gas refrigerant discharged from a compressor is introduced into an evaporator while bypassing a condenser so that air passing through the evaporator is heated by heat from the gas refrigerant. That is, the operation of the refrigerant cycle system is switched so that the evaporator is used as a cooling unit during a cooling mode and is used as a heating unit during the heating mode.
However, in the conventional system, when a refrigerant amount within a hot gas bypass cycle is insufficient, refrigerant staying in the condenser is only recovered. Therefore, even when the refrigerant amount in the refrigerant cycle is greatly reduced due to a refrigerant leakage from a component or a pipe of the refrigerant cycle system, the operation of the compressor is continuously performed. Thus, in this case, the compressor may be damaged.